What is one reason that can make a Certificate of Airworthiness invalid?

One reason that can make a Certificate of Airworthiness invalid is when the aircraft exceeds its maximum gross weight. The Certificate of Airworthiness indicates that an aircraft is fit for flight under its defined limitations, including weight. Each aircraft has a specified maximum takeoff weight, which is crucial for ensuring safety in flight. If an aircraft exceeds this weight, it may affect the aircraft’s performance characteristics, such as lift and control, leading to potential safety hazards. Hence, operating an aircraft beyond its approved weight limits can render the airworthiness certificate invalid. This emphasizes the importance of adhering to weight restrictions in maintaining the airworthiness of an aircraft.